The invention relates to a process for determining the load of an asynchronous motor fed via a frequency converter, and a device for carrying out this process.
German patent document A1-31 01 511 discloses a known process for determining the load of devices, in particular domestic appliances which are driven, inter alia, by an asynchronous motor and which carry out different operating programmes under different load states and in which the operating voltage of the asynchronous motor is controlled by means of an electronic control system containing a microcumputer, the load state determining the respective operating programme is determined by comparing at least one variable supplied by the electronic control system controlling the operating voltage of the asynchronous motor and at least one comparison value predetermined for the asynchronous motor; the phase difference between the operating voltage zero crossover point is used as the variable supplied by the electronic control system and the width of the pulse width signal, supplied by the electronic control system, for the power component of the converter-fed asynchronous motor is used as the manipulated value. In the known case, the zero crossover point of the operating voltage is detected by a zero crossover point detector and the zero crossover point of the operating current is detected by a Hall generator; the phase shift angle which is representative of the load is then detected by the electronic control system which is already present and required even without detection of the load.